To optimize the models for cancer risk assessment of PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs), six models of three types utilized with high frequency in recent years, including the USEPA recommendation (Model I), inhalation carcinogen unit risk (Models IIA–IID), and three exposure pathways (inhalation, dermal, and oral) (Model III), were selected to calculate potential cancer risk using the benzo[a]pyrene toxicity equivalent method. The results indicated no significant differences in the risk values between Models IIA and III, and no significant differences were found among Models IIB, IIC, and IID. However, there were significant differences between Models I and II, and between Models I and III. Furthermore, the optimization of Model I indicated that the population exposure parameters for each country should be used and age differences should not be disregarded. However, no significant differences were observed with respect to gender. In conclusion, Model I was superior to the other models; when age differences were not considered, Model IID (the USEPA's integrated risk information system) was preferred to replace Models IIB and IIC. Models IIA and III may overestimate the risk of carcinogens, and their parameters need to be reoptimized to accurately assess cancer risks.

The PAH concentrations were quantitatively analyzed using gas chromatography-mass spectrometry.

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in PM_2.5